Female pattern hair loss has been widely thought to be the female equivalent of male balding and is often referred to as female androgenetic alopecia. This common condition in women is characterized by a diffuse reduction in hair density over the crown and frontal scalp with retention of the frontal hairline. The prevalence increases with advancing age.
The Role of androgens in androgenetic alopecia in women
The role of androgens in female pattern hair loss is not fully established. Scalp hair loss is undoubtedly a feature of hyperandrogenism in women but many women with female pattern hair loss do not have higher levels of circulating androgens. However, they have been found to have higher levels of 5α-Reductase (an enzyme that catalyzes the irreversible reduction of testosterone to dihydrotestosterone), more androgen receptors, and lower levels of cytochrome P450 (which converts testosterone to estrogen).
DHT Dihydrotestosterone – Androgen 
Testosterone
Clinical features
The most common clinical feature of androgenetic alopecia in women is a gradual thinning of hair over the frontal area, which often occurs over a period of several years. This hair loss can start at any time between the early teens and late middle age. Androgenetic alopecia in women is not usually accompanied by increased shedding of hair, but unlike telogen effluvium, hair thinning is usually noticeable from the onset. As the disease progresses, the scalp becomes more visible.
Examination of the scalp reveals, in most cases, a widening of the central parting with a diffuse reduction in hair density involving primarily the frontal scalp and crown. In some women the hair loss may affect a quite small area of the frontal scalp whereas in others the entire scalp may be affected, including the parietal and occipital regions. Women typically retain a rim of hair along the frontal hairline even when the scalp is visible behind the hairline.
Laboratory evaluation
Most women with androgenetic alopecia have normal menses, normal fertility, and normal endocrine function, including correct levels of circulating androgens. Therefore extensive hormonal testing is only needed when symptoms and signs of androgen excess are present. Laboratory measurement of serum total or free testosterone, dehydroepiandrosterone sulfate and prolactin are appropriate when hirsutism, severe unresponsive cystic acne, virilization, or galactorrhoea are present. Other common causes of hair loss are eliminated by measurement of serum thyrotropin, iron studies including serum iron and ferritin, and complete blood count.
Differential diagnosis
Even though the features of chronic telogen effluvium are distinct, androgenetic alopecia in women can be confused with the former condition. Horizontal sections of a scalp biopsy help to distinguish the two conditions, the ratio of terminal hairs to miniaturized hairs being the indicator.
Morphology
The hairs in androgenetic alopecia become progressively miniaturized with time, both the papillae and matrices, as well as the resulting hair shafts. However, the degree of miniaturization of hair is not uniform or as extreme in most women as in some men. Instead, women with pattern hair loss have a mosaic of variable-diameter hairs in the affected region of the top of the scalp. Increased spacing between hairs makes the central part appear wider over the frontal scalp compared to the occipital scalp. In some cases, hair density appears normal proximally, but the hair no longer grows to its previous length, resulting in thin distal ends. The end result in women with female pattern hair loss is a visual decrease in hair density, vis-à-vis baldness in men, in the affected areas.
Treatment
Because the hair loss in androgenetic alopecia is a result of abnormality of the normal hair cycle, it is theoretically reversible. However, the current treatment options are limited in their action, and modest improvements in hair density are achievable only in some cases. Advanced androgenetic alopecia may not respond to treatment, because the inflammation that surrounds the bulge area of the follicle may have caused irreparable damage to the follicular stem cell. Some treatment regimens include:
- Minoxidil is the currently preferred treatment for androgenetic alopecia and is topically administered as 2 percent Minoxidil. The exact mechanism by which Minoxidil works is not known, but the treatment appears to affect the hair follicle in three ways: it increases the span of time follicles spend in anagen, it rouses follicles that are in catagen and it enlarges the actual follicles. In effect, vellus hairs enlarge and are converted to terminal hairs, and shedding is reduced.
- Earlier, exogenous estrogen was used to treat androgenetic alopecia, but this treatment is used less often now, because of the efficacy of Minoxidil.
- Although Finasteride has been shown to be effective in men with alopecia. The agent should not be used in women of childbearing age, because 5a-reductase inhibitors may cause abnormalities of the external genitalia in the male fetus. Additionally, finasteride has not been shown to be useful in postmenopausal women with androgenetic alopecia.
- Hairstyling, teasing, coloring, permanents, and the use of hair spray are means of coping with the cosmetic effects of androgenetic alopecia. When hair loss is extensive, wigs may be worn.
- Hair transplantation, an accepted treatment for male balding, is increasingly being used in female hair loss, but the expense and trauma involved results in only a small minority of women going in for this avenue of treatment.
- Surgery is most suited to those women in whom hair loss is limited in extent and in women whom medical treatment has been ineffective.
Conclusion
Female pattern hair loss is probably a multi-factorial genetically determined trait and it is possible that both androgen-dependent and androgen-independent mechanisms contribute to this strange form of hair loss. The hair loss in women is usually patterned with most marked thinning over the frontal and parietal scalp, and with greater density over the occipital scalp. Unusual hair loss in women has been found to have significantly detrimental effects on self-esteem, psychological well being, and body image, and it is important that the physician managing patients with androgenetic alopecia should be aware of these adverse effects of this form of hair loss on the quality of life.